Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932618Ab3HNKts (ORCPT ); Wed, 14 Aug 2013 06:49:48 -0400 Received: from 8bytes.org ([85.214.48.195]:50324 "EHLO mail.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932467Ab3HNKto (ORCPT ); Wed, 14 Aug 2013 06:49:44 -0400 Date: Wed, 14 Aug 2013 12:49:38 +0200 From: Joerg Roedel To: Grant Grundler Cc: Tomasz Figa , Cho KyongHo , Linux ARM Kernel , Linux IOMMU , Linux Kernel , Linux Samsung SOC , devicetree@vger.kernel.org, Kukjin Kim , Prathyush , Rahul Sharma , Subash Patel , Antonios Motakis , kvmarm@lists.cs.columbia.edu, Sachin Kamat Subject: Re: [PATCH v9 03/16] iommu/exynos: fix page table maintenance Message-ID: <20130814104938.GF4491@8bytes.org> References: <002701ce941a$eecebdb0$cc6c3910$@samsung.com> <1516548.d7oQuzQS7g@amdc1227> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-DSPAM-Result: Whitelisted X-DSPAM-Processed: Wed Aug 14 12:49:42 2013 X-DSPAM-Confidence: 0.9992 X-DSPAM-Probability: 0.0000 X-DSPAM-Signature: 520b60c620861088910861 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1193 Lines: 28 On Thu, Aug 08, 2013 at 11:28:44AM -0700, Grant Grundler wrote: > I can't speak to the previous BUG_ON(). I believe the EADDRESSINUSE > failures could be either WARN_ON or BUG_ON. This condition is > clearly a bug in the generic IOMMU allocator and I think that's why > KyongHo Cho used BUG_ON. > > Handing out duplicate addresses will generally lead to some sort of > data corruption or other fault depending on how robust the underlying > device drivers are written. So my preference is a BUG_ON to > immediately flag this condition instead of hoping a device driver will > correctly handling the dma mapping failure (Some do, most currently > don't). > > WARN_ON() + return -EADDRESSINUSE would be a good alternative. Even if it is a real BUG condition, I don't think it is worth to stop execution at this point. It makes debugging harder and the system less reliable. I prefer to go with the WARN_ON and an error return value. Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/